1. Field of the Invention
The present invention relates to a liquid phase deposition method for growing a titanium dioxide film on the gallium arsenide substrate, and in particular, to a liquid phase deposition method in which the solution of the hexafluorotitanic acid is added with a nitric acid and a boric acid or is only added with a nitric acid for growing a titanium dioxide film on the gallium arsenide substrate.
2. Description of the Prior Art
Gallium arsenide is most important material in the photoelectric semiconductor since the gallium arsenide has a direct energy gap and a high electron mobility, and it is suitable to fabricate high speed elements or photoelectric elements, for example, field effect transistors, laser diodes, light emitted diode, etc.
The material with higher dielectric constant, such as titanium dioxide film, is widely used in the manufacturing process of the silicon integrated circuit and the structure of semiconductor photoelectric elements of compound, for example:
(1) Since the titanium dioxide has the higher dielectric constant, it can be employed in the high capacity memory of silicon for example, DRAM . . . etc. PA1 (2) Nowadays there are no metal oxide semiconductor field effect transistor (MOSFET) made by gallium arsenide. However, if there is a material with a smaller draining current serves as the gate oxide layer of the MOSFET, it is probable to develop that kind of element. PA1 (3) Since the titanium dioxide has a higher refractive index, it can be matched with material of the lower refractive index to apply to waveguides, optic filters, antireflecting coatings and other semiconductor elements of photoelectric compounds. PA1 (1) Reactive sputtering; PA1 (2) Sol-gel growth in a temperature of 800.degree. C., and PA1 (3) Low pressure chemical vaporizing deposition (PECVD) in a temperature of 400.degree. C. PA1 (1) MOSFET: In the elements of galliumn arsenide, if a material with a low drain current serves as the gate oxide layer of a MOSFET, the applications of the MOSFET can be enlarged. PA1 (2) Photoelectric elements: Titanium dioxide has a higher refractive index, thus it can match with the material with lower refractive index, for example, silicon dioxide, so as to be employed in the photoelectric elements, such as waveguides, optic filters, anti-reflecting coatings, etc. PA1 (3) Masking: Titanium dioxide has an erosion-tolerance property, it can be a mask of semiconductor elements of photoelectric compounds. PA1 (a) providing a general gallium arsenide chip as a substrate; PA1 (b) adding a nitric acid or a boric acid or only adding a nitric acid to the solution of the hexafluorotitanic acid for growing a titanium dioxide film on the gallium arsenide substrate.
Further, a mask is necessary in manufacturing gallium arsenide high speed element or photoelectric element, such as field effect transistors, laser diodes, light emitted diodes, etc. However, since gallium arsenide has no its own oxide layer to serve as a mask, thus the most frequently used methods of growing a titanium dioxide are:
The high radiation from the sputtering will harm the elements during fabricating elements on the other hand, the high temperatures in the sol-gal and PECVD are also harmful to the elements. Further, the growth equipment is very expensive, thus the cost is increased.
Accordingly, the aforementioned prior arts have many defects, which is necessary to be improved.